The present invention relates generally to infusion devices, systems and processes and, in particular embodiments to implantable infusion devices, systems and processes employing a drive mechanism configuration which allows the device to have a relatively thin form factor and use power efficiently. Further embodiments of the invention relate to drive mechanisms and processes of making and using such drive mechanisms for infusion devices and systems.
Infusion devices are typically used to deliver an infusion media, such as a medication, to a patient. Implantable infusion devices are designed to be implanted in a patient""s body, to administer an infusion media to the patient at a regulated dosage.
Because implantable infusion devices are designed to be implanted in the patient""s body, the dimensions of such devices can have an impact on the determination of the location in the body at which a device may be implanted, the level of comfort of the implant patient and the external appearance of the implant site. Typically, a device with relatively small dimensions and, in particular, a relatively small thickness form factor, will provide greater flexibility in the choice of location in the patient""s body to place the implant and will minimize patient discomfort and minimize noticeable protrusions at the implant site. Accordingly, there is a demand in the industry for minimizing the overall dimensions, and, in particular, the thickness dimension of implantable infusion device.
In some contexts of use, the infusion device must be operable for an extended period with a limited power supply. For example, battery powered infusion devices may be implanted in or otherwise connected to patients, to deliver medication at controlled intervals over a prolonged period of time. In some devices, when the batteries die, the devices are simply thrown away. Also, as the battery power supplies for such devices have limited capacities, some devices typically require multiple replacements of batteries over their operational life. There is a demand in the industry for infusion devices which make efficient use of power supplies and, thus, require fewer or no power supply replacements. This demand is particularly important for implantable devices, which may require surgical removal to replace depleted power supplies.
Accordingly, embodiments of the present invention relate to infusion devices and drive mechanisms for infusion devices which address the above-mentioned industry demands.
Preferred embodiments of the invention relate to such devices and drive mechanisms configured for implantation in a patient""s body. Configurations described herein allow the drive mechanism and, thus, the infusion device to have a relatively small thickness dimension, for example, to minimize trauma to the implant recipient (referred to herein as the patient).
Further preferred embodiments relate to such devices and drive mechanisms configured and operated to make highly efficient use of electrical power to prolong operational life.
Yet further preferred embodiments relate to such devices and drive mechanisms configured to deliver relatively precisely controlled volumes of infusion medium, within a relatively wide range of volumes, including relatively small volumes.
Yet further preferred embodiments relate to such devices and drive mechanisms configured to deliver sufficiently precise volumes of relatively high concentration infusion medium.
An infusion device according to an embodiment of the invention includes a generally disc-shaped housing made from a biocompatible and infusion medium compatible material. The infusion device housing contains a reservoir for holding a volume of infusion medium, such as, but not limited to, a medication to be administered to the patient. The infusion device housing has an outlet through which the infusion medium may be expelled.
The infusion device further includes a drive mechanism having an inlet coupled in fluid flow communication with the reservoir and an outlet coupled in fluid flow communication with the infusion device housing outlet. In one embodiment, a filter may be disposed between the reservoir and the drive mechanism (or as part of the inlet of the drive mechanism). In a further embodiment, expandable and compressable devices, such as one or more volume compensators or accumulators, which may also be, for example, accumulators, also may be disposed in the flow path between the reservoir and the drive mechanism inlet, to dampen surges and ebbs in the flow.
The drive mechanism employs electromagnetic and mechanical forces to move a piston between retracted and forward positions or states, to cause infusion medium to be drawn from the reservoir, through an inlet and forced out of an outlet. A drive mechanism, according to one embodiment, comprises an assembly of components which may be manufactured and assembled in a relatively cost efficient manner. The components include a housing containing a coil disposed within a coil cup, a piston channel surrounded by the coil, a piston extending through the piston channel, an armature disposed at one end of the piston channel and an outlet chamber with a valve assembly disposed at the other end of the piston channel.
When the coil is in a quiescent state, the armature and piston are urged toward a retracted position by mechanical or magnetic forces. When the coil is energized, the armature and piston move to a forward stroke position. The movement of the piston from a retracted position to a forward position creates pressure differentials within the drive mechanism to drive medium out the outlet. Mechanical force may return the piston to the retracted position. The movement of the piston from a forward position to a retracted position creates pressure differentials to draw medium into the drive mechanism inlet.
Embodiments of the invention employ a coaxial arrangement of the piston, the piston channel and the coil, to provide significant advantages with respect to providing a relatively thin form factor and efficient power usage. A number of features can each provide or be combined to contribute to a reduction in the thickness form factor of the drive mechanism. For example, a coaxial arrangement of components can be implemented with a smaller thickness form factor than alternative arrangements in which components are arranged in series with each other in the thickness dimension. Embodiments may include an inlet volume on one side of the coil and an outlet chamber on the opposite side of the coil, with a flow passage through the piston channel, such that the coil and flow channel share a common portion of the thickness dimension. The armature may be located within the inlet volume and, thus, share a common portion of the thickness dimension with the inlet volume. The outlet chamber may be centrally located within the same housing that has the coil cup and formed in relatively close proximity to the coil cup in the thickness dimension of the housing.
Further embodiments may include an outlet port and one or more fluid flow damping or accumulator structures, such as pillows or accumulators in pillow or accumulator cavities, in the housing, to help provide a relatively stable, constant output pressure during drive operations. The accumulator cavities, outlet port and outlet chamber may share a common portion of the thickness dimension of the drive mechanism, to maintain a relatively thin form factor.
In addition, a number of features described herein can provide, or be combined to contribute to, the efficient use of power to, prolong the operational life of the drive mechanism. One manner of improving the operational life of an infusion device according to embodiments of the present invention, is to lower the power consumption requirements of the drive mechanism by employing a coaxial coil and piston configuration and one or more features for making highly efficient use of electromagnetic energy. Another manner of improving the operational life of a device according to embodiments of the invention is to reduce the number of operations of the drive mechanism required over a given period of time, by pumping reduced volumes of a higher concentration infusion medium (an infusion medium with a higher concentration of active ingredients) or pumping higher concentration volumes at reduced intervals.
These and other aspects and advantages of the invention will be apparent to one of skill in the art from the accompanying detailed description and drawings.